An evo-devo geek's scientific meanderings

physics and astronomy

Scientific American online made me smile today. I get the newsletter; I don’t usually read it, because the SciAm website ranks somewhere between Cracked and TVTropes on the scale of time sinks. I hardly need another chance to procrastinate. Anyway, for some reason I did open several articles this morning. One of them was headlined “Earth’s Days Are Numbered,” and of course I clicked the link for the opportunity to grump, because I was pretty darn sure that the title was pure sensationalism and I’m mean like that.

I was right. Right after the headline, the article (which they borrowed from Nature) warns us of the impending catastrophe thus: “Researchers calculate that the planet will leave the sun’s “habitable” zone in about 1.75 billion years.”

Yeah. Should I laugh or should I cry? (I have to say I laughed. I must be in an uncharacteristically charitable mood today.)

But then I read the whole thing, because my officemate started wondering what would kill poor earth in 1.75 billion years, and that made me wonder. Was it orbital instability, or was it just grumpy old Sol getting hotter and roasting us? (To spare you the suspense: it was the sun.)

The article closes with a quote from one of the folks who did the maths. A really sweet, naive, optimistic quote. A quote that makes you think this guy would never ever write dystopian sci-fi. Here’s the last paragraph and the quote:

Just as the sun brightens and the Earth becomes too hot for life, Mars will be entering the habitable zone. “If humans are going to be around in a billion years, I would certainly imagine that they would be living on Mars,” Claire says.

I… just… awwww!

Maybe I’m a cynic. (No, scratch that “maybe”.) But I’m also an evolutionary biologist and have more than a passing familiarity with the history of life. If you show me a species of animal that survived even for a hundred million years, never mind a mammal that lasted a billion, I’ll be impressed*.

(Of course, there could be a chance that the human lineage draws the jackpot and survives. Technically,cladistically speaking, maybe, all of our descendants should be called humans. “Human” is a colloquial term, not a clade name, but let’s forget that for a moment. Even so, I’ll bet you my beloved hat that whatever’s left of us in a billion years would only be “human” in technicality.)

Even though I should probably rage at the way these guys make it sound like humans being around in a billion years is a plausible idea, it only kindles a strange fuzzy kind of warmth around my shrivelled little heart. There go my principles… 😉

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*No, “living fossils” don’t last billions of years. Don’t get me started on living fossils.

Squee number one: Dumusque et al. (2012) found a probably earth-sized planet literally next door to the solar system. The newly announced rockball orbits α Centauri B, one of the three(?)* stars making up the star system closest to the sun. Alas, it’s unlikely to harbour life of any kind given its very close orbit – it goes around a star not much cooler than our sun in slightly over 3 days. However, the authors point out that small planets are most likely to be found in multiplanet systems, and given the difficulty of finding this one, the star may well have even harder to detect, more distant companions. I think this is a nice reminder of how much more we need to learn about other solar systems – this little guy has been circling there, a mere four point something light years from us, and we only found it now. Keep it up, planet hunters, you’re doing amazing stuff!

*I’ll let the real astronomers argue whether Proxima Centauri is part of the α Centauri system…

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Squee number two: I totally must read this book. It’s the ultimate evo-devo book: it’s about fossilised development, basically. It seems overwhelmingly vertebrate-centred based on the review in Developmental Dynamics, but hey, there is an invertebrate chapter and I take what I can get 😀

And wow, it’s not even that expensive as far as university-published hardcover sciencey books go! Hmm. Shall we give in to temptation right now or save it for a Christmas present?

Back when Star Wars was new – and even when the new trilogy was new -, a planet orbiting more than one star was nothing more than speculation. (Though back when SW was new, even a planet orbiting another star was little more than speculation.)

I’m excited to see that the Kepler team are busy turning it into solid reality. They now have not one, not even two, but three planets that they found around binary stars (the first was described a few months back [Doyle et al., 2011]; the other two are just online [Welsh et al., 2012]). None of them are particularly Tatooine-like, alas, since all are gas giants, but given how hard small planets are to find, we can be fairly confident that we’ve just overlooked them so far.

All three planets orbit in the same plane in which their stars orbit each other, indicating that the whole system formed from the same rotating disc of space debris. Based on the number of star pairs they’ve looked at so far and the chance of observing planetary transits in binary systems like Kepler-16, 34 and 35, Welsh et al. estimate that millions of similar systems could be hiding in the Milky Way alone.

To top it off, another new Nature paper (Cassan et al., 2012) reports that in fact, most sun-like stars in the galaxy are likely to have planets.

A truly astronomical number of strange new worlds are out there. How many of them could harbour life?

(Can you hear my inner geek squealing with joy? :D)

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References

Cassan A et al. (2012) One or more bound planet per Milky Way star from microlensing observations. Nature481:167-169

It’s a little-known fact that before/in between wanting to be a biologist, I almost got sucked into astronomy. The cosmos still fascinates me, from the menagerie of space rocks and gas balls that fill our own solar system to the mysteries at the edge of the known universe. To the evolutionist in me, the possibility of life on other worlds is an especially tantalising idea. And now we are finding other worlds at a breakneck pace. I don’t think we will ever know what life is like on any of them, though detecting its existence may once become possible.

Did I mention planet hunting is awesome?

I am talking about the citizen science project Planet Hunters, of course. This is only one of the amazing projects you can participate in at the Zooniverse (which gets its name from Galaxy Zoo, the project that started it all). The main mission of Planet Hunters is, of course, to find planets orbiting other stars. You, the user have to look at a month’s worth of brightness measurements from a star, and search for the tell-tale dips that betray an extra-solar eclipse. Like this:

Most of the more spectacular ones have already been found by this point – either by your fellow hunters, or by the team operating the Kepler space telescope, which provides all the data. However, there are so many other gems to discover among those messy light curves that it almost doesn’t matter if your planet-hunting thunder is perpetually stolen.

Sometimes, you find pure beauty. One of the most common types of Interesting Stuff that the Kepler data offer is eclipsing binaries. These are pairs of stars orbiting each other in a way that we see their orbits edge on. Like the planets, these binaries eclipse their companion stars. Since stars are bigger and brighter than planets, the eclipses are much bigger compared to the noise in the data, so an EB has neat, clean dips in its light curve, occurring with clockwork regularity.

Some of them are so close together and orbit so fast that at Kepler’s resolution, a month of their light looks more like lace than a pattern of ups and downs.

And then there are all the others; dwarfs and giants, variable stars regular and haphazard, huge flares, weird things like cataclysmic variables. Even if you are in it for the planets, you can’t help but learn a lot about the stars. After a while, they become like family. You look at a light curve and you can immediately guess whether it’s a dwarf or a giant, whether it’s cool or hot, whether it’s a binary or a loner, or even if its’s one of the rarer breeds of stars you might come across. It’s a bit like birdwatching. If you’ve ever got disproportionately excited from recognising a rare bird (or flower, or insect, or sports car), you know what I mean. (If you haven’t, what are you waiting for? ;))

I’m grateful to the people who make these adventures possible. It’s great that I can play at astronomy, see all that neat stuff, contribute to a field I have absolutely no expertise in, and learn from the knowledgeable folks that hang around the forums. The Zooniverse deserves every one of its hundreds of thousands of users and millions of clicks, is all I’m saying 🙂